1. Technical Field
The present disclosure relates to voice coil motors, and, more specifically, to a multi-axis voice coil motor with reduced thickness or volume.
2. Description of Related Art
With a continuous demand for less weight and less thickness of the lens set in cameras or wearable cameras, there are increasing needs for thin lens module which has a thickness less than 3.5 mm. On the other hand, with the improvement of the optical image stabilization technology, the number and size of optical actuator increase. Therefore, there are multiple technical bottle necks for designing a multi-axis actuator today.
The foregoing challenges include the difficulty in the design of multi-axis actuator itself and the production quality. The problems of designing multi-axis actuator include how to simultaneously provide auto focus (AF), the 3-5 axis directions required for OIS, as well as to keep the thickness under 4 mm. The challenges in production on the other hand include how to design a simple process to achieve an automatic manufacturing with high precision, speed and able to satisfy the yield requirement. Moreover, the thickness of the cell-phone camera module (CCM) has always been a focus for development which has gone from a few dozen mm to 7-8 mm now. The AF actuator moves in one parallel direction along the optical axis, allowing the lens to move about 0 to 0.5 mm to focus on the object. The OIS actuator moves in a least 2 vertical directions along the optical axis to compensate the displacement motion (<±0.2 mm) or rotational movement (<±0.4°) caused by camera shakes. Generally, a camera module with OIS function also has AF function, which is achieved by mounting actuator elements below the AF actuator, which moves along 2-4 axis directions, and using the gyroscope to measure the selectively configured two motion displacement/tilting or 2 motion displacement and 2 tilting in more advanced setting to calculate the compensated displacement motion. Since the required number for optical actuators increases to 3-5 optical actuators, the overall thickness of the module also undesirably increases. The miniaturized elements and increasing number of actuators dramatically increase the difficulty in manufacturing and set a series of technical challenges in the field.
In order to satisfy 5 axis micro-optical actuator (MOA) required for AF and OIS, the commonly used voice coil motor (VCM), though having the advantages of high yield, low cost, simplicity in structure and high reliability, would cause the overall thickness to increase 2 mm when axis number increased from 3 to 5. Therefore, it would be difficult to be accommodated in the product without protruding from the product surface. In manufacturing, CCM mainly consists of lenses, IC circuit and VCM. Since the module is reduced in size, the volume of the lenses and VCM is also reduced, which results in problems such as malfunctions in lenses and low assembly yield.
Accordingly, there is an urgent need in the CCM field to develop an image module which is thin and capable of producing high quality image with increasing axis directions without increasing the thickness.